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Extinct frog hops back into the gene pool

Nicky Phillips

In what may be considered an early Easter miracle, an extinct species of native frog has begun its rise from the dead.

Australian scientists have grown embryos containing the revived DNA of the extinct gastric-brooding frog, the crucial first step in their attempt to bring a species back to life.

The team from the aptly named Lazarus project inserted the dead genetic material of the extinct amphibian into the donor eggs of another species of living frog, a process similar to the technique used to create the cloned sheep Dolly. The eggs continued to grow into three-day-old embryos, known as blastulas.

Extict since 1983: The bizarre gastric-brooding frog.

"This is the first time this technique has been achieved for an extinct species," said one of the project scientists, conservation biologist Michael Mahony.

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While many scientists have argued it would be impossible to bring a species back from the dead like in the film Jurassic Park, the Lazarus project's breakthrough suggested the revival of extinct species was no longer the realm of science fiction.

Over five years the team led by University of NSW palaeontologist Mike Archer painstakingly inserted DNA extracted from a frozen specimen of the bizarre gastric-brooding frog, which incubated its eggs in its stomach before giving birth through its mouth, into hundreds of donor eggs from a distant relative, the great barred frog, whose DNA had been deactivated by UV light.

Frozen for 40 years

In the beginning, the single cell eggs "just sat there", said Professor Archer. "But then, all of a sudden, one of the cells divided, and then it divided again, and again.

"There were a lot of high fives around the laboratory at that point," said Professor Archer, who was to announce the team's achievement at the TEDxDeExtinction event in Washington on Friday.

While the embryos had yet to develop into tadpoles, genetic tests revealed the dividing cells contained the DNA of the extinct frog.

The egg donor frog.

"We do expect to get this guy hopping again," Professor Archer said.

The team has also demonstrated that the cloning technique, known as somatic nuclear cell transfer, could be used to conserve the genomes of other critically endangered species, particularly frogs, whose populations have plummeted around the world.

"We haven't brought back the gastric-brooding frog yet but we've developed a tool that can stop other frogs going extinct," said Professor Mahony, from the University of Newcastle.

Determined to bring the species back to life: Professor Michael Archer. Photo: Marco Del Grande

But the team's success so far did not come easily.

"It's not as if we're following a recipe," said Professor Archer.

The project would have remained a science fiction fantasy were it not for the foresight of Adelaide frog researcher, Mike Tyler, who froze a gastric-brooding frog specimen before it disappeared from the wild in 1979 and became extinct in 1983.

"It's a minor miracle that a university freezer hasn't been turned off in a power failure," Professor Archer said.

The leader of the technical work, Monash University reproductive biologist Andrew French, said it was also amazing the team was able to extract viable DNA from the dead frog's cells.

The annual breeding cycle of the donor egg frog also meant the team had only a few weeks a year to conduct their experiments, Dr French said.

While the results are yet to be published, the group felt it was time to talk about their success.

"We thought it was probably time to put the flag in the sand," said Professor Archer, who has previously directed attempts to revive the extinct Tasmanian tiger.